DE69019912T2 - Absorbent hygiene product. - Google Patents

Abstract

A distinctive absorbent garment article (10) generally delimits a front waistband section (12), a rear waistband section (14) and an intermediate section (16) which interconnects the front and rear waistband sections. The article comprises a substantially fluid-impermeable backsheet layer (20), a liquid permeable topsheet layer (70), positioned in facing relation with the backsheet layer, and an absorbent body (40) located between the backsheet layer and topsheet layer. The absorbent body includes a distinctive humidity transfer region which is advantageously configured to exhibit relatively low moisture retention. A vapor permeable panel (70) is connected to the backsheet layer at one or more waistband sections of the article, and is arranged in an overlying registry with the humidity transfer region of the absorbent body (10).

Description

The present invention relates to an absorbent article, particularly a garment for absorbing body fluids and exudates such as urine. More particularly, the present invention relates to absorbent garments, such as disposable diapers and adult incontinence garments, designed to absorb body exudates while contributing to reduced hydration of the skin.

Breathable polymer films have been used as outer covers for absorbent garments such as disposable diapers. The breathable films are typically designed with micropores to provide the desired degree of liquid impermeability as well as vapor permeability. Other disposable diapers have been designed to provide a certain degree of breathability at the leg cuff areas of the diaper. An example of this is U.S. Patent No. 4,636,207 issued to K. Buell on January 13, 1987.

Perforated areas have been used in diapers and plastic pull-on pants that cover the diapers to aid in the ventilation of the garment. Examples of this are shown in U.S. Patent No. 3,081,772, issued March 19, 1963 to H. Brooks et al. and U.S. Patent No. 2,544,069, issued March 6, 1951 to H. Cutler.

EP-A-0 269 401 discloses an absorbent garment with absorbent means and two air-permeable flaps. The Absorbent means comprise a liquid permeable layer, a liquid impermeable layer and an absorbent layer therebetween, the absorbent means. The garment ventilates the absorbent layer by circulating air around the air permeable flaps. The flaps are connected to the absorbent means and thus serve to remove moisture from the interior of the garment and to evaporate moisture from an area around a waistband portion of the garment. The flaps also form an outer surface of the garment and thus bring it into contact with the outer garments of the wearer. Therefore, contamination of the outer garments is possible. In addition, moisture can reach the ventilation area due to gravity (as is the case with a sleeping child in a lying down position) and thus seep through the outer garments.

GB-A-2 171 915 describes a panty liner with ventilation areas which allow vapour permeability to achieve a cooling and drying effect; and GB-A-2 115 702 describes an absorbent article with a porous, vapour permeable liquid impermeable backing layer.

U.S. Patent No. 4,341,216 issued to M. Obenour on July 27, 1982 describes a disposable diaper having a breathable backsheet comprising two elements. The two elements are a vapor permeable, relatively liquid impermeable outer layer and a liquid impermeable inner layer.

Other forms of disposable garments have additional layers of material underneath the body-facing Pad. European Patent Application EP 0 165 807 A1 by T. Osborn III, published on December 27, 1985, describes a sanitary napkin having an apertured top layer and an elastic reservoir layer beneath the top layer. The absorbent structure may also include a layer of wicking material between the apertured top layer and the elastic layer, an absorbent core beneath the elastic layer, and a moisture barrier on the outermost side of the absorbent core.

Various types of diaper structures have used hydrophilic wicking layers to direct fluid within an absorbent structure. Examples are given in U.S. Patent No. 4,388,371, issued July 6, 1982 to F. Dawn et al.; U.S. Patent No. 4,259,958, issued April 7, 1981 to R. Goodbar; and UK Patent Application GB 2 170 108 A, published July 30, 1986, to L. Bowman et al.

Other diaper designs have used embossed layers designed to provide raised areas separating the user from the absorbent pad. See, for example, U.S. Patent No. 4,324,247, issued April 13, 1986 to M. Aziz; U.S. Patent No. 4,041,951, issued August 16, 1977 to L. Sanford; U.S. Patent No. 3,945,386, issued March 23, 1976 to E. Anczurowski et al.; and U.S. Patent No. 4,413,032, issued November 1, 1983 to L. Hartmann et al.

Similarly, disposable absorbent articles have used a layer to separate a top layer from an absorbent layer. For example, GB 2 193 625 A by M. Suzuki et al., published on 17 February 1988, includes a layer made of polyester fibres for separation at a selected pressure resilience recovery rate under wet conditions. U.S. Patent No. 4,480,000 issued October 30, 1984 to I. Watanabe et al. describes an absorbent article having a web made of polyester fibers disposed on an absorbent core layer. According to the description, the absorbent article has an improved fluid absorption rate and still feels dry even after such absorption.

U.S. Patent No. 3,987,792, issued October 26, 1976 to J. Hernandez et al., describes a disposable diaper having a water permeable layer, a spongy, resilient and compressible hydrophobic fiber layer, an absorbent core and a water impermeable layer. The hydrophobic fiber layer is fluid permeable when uncompressed, but is fluid impermeable when compressed. The description shows that the hydrophobic fibers interlock when compressed to form a seal or barrier.

Conventional absorbent articles such as those described above have not been found to be entirely satisfactory. For example, articles with a microporous outer shell may produce a feeling of coldness and clammy stickiness when the garment is wetted and moisture evaporates through the microporous film. Articles with perforated films may result in excessive leakage of liquids from the article and excessive contamination of the wearer's outer garments. In addition, when the absorbent material of the article is loaded with liquid, the wet absorbent may block the escape of moisture from the wearer's skin. Other forms of absorbent garments with additional layers between the The bodyside liner layer and absorbent core layer failed to sufficiently reduce the hydration of the wearer's skin. As a result, the wearer's skin remained susceptible to abrasion and continued to become easily sore.

The present invention provides an absorbent article according to independent claim 1. Further advantageous features of the article are apparent from the dependent claims, the description, the drawings and the examples. The claims are to be understood as a first, non-limiting attempt to generally describe the invention. The invention provides a disposable diaper having a moisture transfer region, a breathable zone panel and a release liner.

The present invention provides a distinctive absorbent article generally defined by a front waistband portion, a rear waistband portion, and an intermediate portion connecting the front waistband portion to the rear. The article includes a substantially fluid impermeable backsheet (backsheet), a liquid permeable topsheet disposed opposite the backsheet, and an absorbent body disposed between the backsheet and the topsheet. The absorbent body has a moisture transfer region configured to have a relatively low moisture retention capacity. A vapor permeable web is bonded to the backsheet in at least one waistband portion of the article and disposed overlying it in registration with at least a portion of the moisture transfer region of the absorbent body.

According to another aspect of the present invention, the absorbent article is generally defined by a front waistband portion, a rear waistband portion, and an intermediate portion connecting the front waistband portion to the rear. The article comprises a substantially fluid impermeable backsheet, a liquid permeable topsheet positioned opposite the backsheet, and an absorbent body positioned between the backsheet and the topsheet. Disposed between the topsheet and the absorbent body are spacer means, such as one or more liquid permeable separating layers configured to facilitate rapid fluid transfer between the topsheet and the absorbent body. The separating layers are made of a substantially hydrophobic material and have a total bulk thickness of at least about 0.04 cm (measured at a pressure of 0.0207 kPa). A vapor permeable panel is bonded to the backsheet at a waistband portion of the article and disposed thereover in register with at least a portion of the absorbent body.

The article according to the invention can advantageously better separate the wearer's skin from the absorbent body. In addition, the absorbent article can ensure more effective dissipation of water vapor from the wearer's skin and from the interior of the absorbent article. Therefore, the article according to the invention can advantageously reduce the wetness of the wearer's skin (reduced hydration of the skin) and ensure reduced susceptibility to skin abrasion and skin soreness. The occlusive and wetting effect of the wet absorbent body can be reduced more effectively and increased comfort can be created for the wearer. In addition, the special form of the invention can reduce the damp cold feeling on the outer surface of the article, which occurs when using back layers made of can advantageously reduce the risk of irritation that typically occurs with breathable films.

By reference to the following detailed description of the invention and the accompanying drawings, the invention will be more clearly understood and further advantages will become apparent.

Fig. 1 representatively shows a partially cutaway top view of an absorbent article according to the invention;

Fig. 2 shows a representative exploded view of an absorbent article according to the invention;

Fig. 3 representatively shows a partially cutaway top view of an absorbent article having a moisture transfer region;

Fig. 4 shows a schematic, partially sectioned representation of a device for measuring the test values of relative humidity;

Figs. 5, 5A and 5B representatively show an apparatus for determining a moisture retention index;

Fig. 6 representatively shows an apparatus for determining a wicking index;

Fig. 7 representatively shows a partially sectioned view of a disposable diaper having an absorbent composite with a moisture transfer region;

Fig. 8 shows a representative view, partially divided into sections, of an embodiment of an absorbent body, in which in which the moisture transfer area is in the shape of a circle;

Fig. 9 shows representatively a partially sectioned view of another embodiment of an absorbent body with a moisture transfer region made of a multi-layer composite material;

Fig. 10 shows a representative view, partially divided into sections, of an embodiment of an absorbent body in which the moisture transfer area is in the form of a notch; and

Fig. 11 is a graphical representation which shows representatively the water vapor transfer rate as a function of the amount of liquid entering the absorbent body.

In the following detailed description, reference will be made to the article of a disposable diaper. However, it will of course be apparent that the absorbent structure of the present invention would also be suitable for other absorbent articles such as feminine hygiene pads, incontinence garments and the like.

Referring to Figures 1 and 3, a unitary absorbent garment article such as a disposable diaper 10 is generally defined by a front waistband portion 12, a rear waistband portion 14 and an intermediate portion 16 connecting the front waistband portion to the rear. The front and rear waistband portions comprise the general areas of the article which are adapted to extend substantially over the front and rear abdomen regions of the wearer, respectively, in use. The intermediate portion of the article comprises the general area of the article which is designed to extend across the crotch region of the wearer between the legs. The absorbent article further includes a substantially fluid impermeable backsheet (backsheet) 20 and a liquid permeable topsheet 30 disposed opposite the backsheet 20, and an absorbent body 40, such as an absorbent pad, is disposed between the backsheet and the topsheet. The absorbent body 40 includes a moisture transfer region 44 (Fig. 3) designed to have a relatively low moisture retention capacity. A vapor permeable panel, such as a breathable panel 70, is substantially liquid impermeable and operably joined to the backsheet 20 to extend partially or entirely across at least a waistband portion of the diaper 10. The breathable panel may be an integral portion of the backsheet or a separate piece attached to the backsheet. The breathable web 70 is, for example, made of a material having a moisture vapor transmission rate (WVTR) of at least about 2000 g/m²/24 hrs. In the illustrated embodiment, at least a portion of the breathable web is disposed in a generally adjacent, overlying and opposing manner in register with the moisture transfer region 44 of the absorbent body 40.

In a particular embodiment of the invention, spacers such as one or more liquid-permeable separating layers 50 may be located between the upper layer 30 and the absorbent body 40, the separating layers being designed to readily allow fluid transfer between the upper layer and the absorbent body. The separating layers 50 may be made of a substantially hydrophobic material. and have a total bulk thickness of at least about 0.04 cm (measured at a pressure of 0.207 kPa).

Edge areas of the diaper 10, such as edge portions of the pad 20, may extend beyond the end edges of the absorbent body 40. For example, in the embodiment shown, the pad 20 extends outwardly beyond the end edges of the absorbent body 40 to form side edges 26 and 28 and end edges 22 and 24 of the garment. The top layer 30 is generally coextensive with the pad 20, but may optionally cover an area that is larger or smaller than the area of the pad 20 as desired.

The diaper 10 may have a variety of suitable shapes. For example, the diaper may have a generally rectangular shape, a T-shape, or approximately the shape of an hourglass. In the illustrated embodiment, the shape of the diaper 10 is generally an I.

The various parts of the diaper 10 are integrally joined together using various types of suitable attachment means, such as adhesives, sonic bonds, thermal bonds, or combinations thereof. In the embodiment shown, the topsheet 30 and the backsheet 20 are joined together and attached to the absorbent body 40 by, for example, line-form adhesives, such as a pressure-sensitive hot melt adhesive. Similarly, other parts of the diaper, such as the elastic members 60, 64 and 66 and the fastener members 36, can be incorporated into the diaper using the attachment mechanisms set forth above.

The illustrated embodiment of the diaper 10 includes ear-like regions 48 extending laterally along the transverse direction 90 of the diaper and located at least on the rear waistband portion 14 of the diaper 10. The ear-like regions 48 may also be located on the front waistband portion 12 of the diaper. The ear-like regions may be integral with the backsheet 20 or may comprise separate portions made of the same or different material as the backsheet 20 and suitably joined and attached to the backsheet. The ear-like regions 48 typically provide extensions of the waistband of the diaper, suitable for completely enclosing the wearer's waist during use.

Fasteners, such as adhesive tapes 36, are used to attach the diaper to the wearer. Alternatively, the use of other fastening means, such as buttons, pins, snap fasteners, hook fasteners, fasteners with a receiving and protruding part or the like, is possible.

To provide improved fit and to help reduce leakage of body exudates from the diaper 10, the side edges and end edges of the diaper may be elasticized with suitable elastic members, such as single or multiple elastic strands. The elastic strands may be made of natural or synthetic rubber and may be optionally heat-shrinkable or heat-elasticizable. The elastic members 60 are designed to operably gather and gather side edges 26 and 28 to provide elastic leg bands that can snugly encircle the wearer's legs to reduce leakage and improve comfort and wearability. Similarly, to provide elastic waistbands, waist elastics 64 and 66 may be used to elasticize the end edges 22 and 24 of the diaper. The waist elastics are designed to operably gather and gather the waistband portions to provide an elastic, comfortable, snug fit about the wearer's waist. In the figures, the elastics are not shown gathered in their stretched state for clarity.

The backing layer 20 is made of a substantially fluid impermeable material which is substantially impermeable to liquid or gas. In particular, the backing is substantially impermeable to at least water and water vapor. An example of a suitable backing material is a polymeric film of polyethylene, polypropylene, or the like. Typically, the thickness of the polymeric film is in the range of about 0.0018-0.0051 cm (0.0007-0.002 inches). The backing 20 may alternatively be made of a nonwoven fibrous web designed to provide the required degree of fluid impermeability. For example, a nonwoven web of spunbond or meltblown polymeric fibers may optionally be treated with a water repellent coating or laminated with a fluid impermeable polymeric film. In a particular embodiment of the invention, the backing 20 may comprise a nonwoven web of a plurality of randomly located hydrophobic thermoplastic meltblown fibers sufficiently bonded or otherwise joined together to provide a substantially vapor impermeable and substantially liquid impermeable web. The backing may also comprise a vapor permeable nonwoven layer which has been partially coated or otherwise designed to provide liquid impermeability in selected areas.

For the purposes of the present invention, a substantially liquid impermeable material is designed to allow no more than about 0.05 ml of water to pass through it within 5 seconds of applying a static pressure head of 70 cm of water to the material. Likewise, for the purposes of the present invention, a substantially fluid impermeable or vapor impermeable material is designed to provide a water vapor transmission rate (WVTR) of no more than about 30 g/m²/24 hours. A suitable method for determining the WVTR value is the WVTR test, which is described in more detail below.

The topsheet 30 is typically made of a liquid permeable, substantially hydrophobic fibrous material, such as a spunbonded web of synthetic polymer filaments. Alternatively, the topsheet 30 may comprise a meltblown web or a bonded carded web of synthetic polymer filaments. Suitable synthetic polymers include, for example, polyethylene, polypropylene and polyester. In accordance with a particular aspect of the invention, the polymer filaments have a denier in the range of about 0.167 tex (1.5 d)-0.78 tex (7d), and preferably have a denier in the range of about 0.167 tex-0.33 tex (1.5-3d) to improve effectiveness. The filaments are arranged to form a layer having a basis weight in the range of about 20-34 g/m², and are preferably arranged to have a basis weight in the range of about 27 g/m². In addition, the top layer has a bulk density in the range of about 0.0203-0.0432 cm (about 0.008-0.017 inches), and has preferably has a bulk density in the range of about 0.0254-0.305 cm (about 0.010-0.12 inches) to improve effectiveness. Bulk density is measured at a retention pressure of 0.096 kPa (0.014 psi).

To regulate its hydrophobicity and wettability, the upper layer 30 can optionally be treated with surface-active substances. It can also optionally be embossed or provided with openings through individual slots or holes 21 extending through it.

The absorbent body 40 typically comprises a pad of air-laid cellulosic fibers, commonly known as wood pulp fluff. Other natural fibers, such as cotton, may also be used to form the pad. Conventional absorbent pads may have a density in the range of about 0.05-0.20 g/cc and are sufficiently elastic to readily conform to the wearer's body. The absorbent body 40 may also comprise a composite material of a blend of cellulosic fibers and synthetic polymer fibers. For example, the composite material may be made from an air-laid blend of cellulosic fibers and meltblown polyolefin fibers, such as polyethylene and/or polypropylene fibers. Specific examples of the composite material include 2-15 weight percent polyethylene and/or polypropylene fibers. According to one aspect of the invention, the fiber material comprising the absorbent body 40 is made of filaments having a coarseness of about 10-20 mg/100 m and preferably a coarseness in the range of about 10-18 mg/100 m. The filaments are arranged to form a layer having a basis weight in the range of about 400-1200 g/m², preferably a basis weight of about 800 g/m². In addition, the bulk density of the absorbent body material, measured at a retention pressure of 0.47 kPa (0.068 psi), is typically in the range of about 0.432-0.533 cm (about 0.17-0.21 inches).

The absorbent body 40 may also include an effective amount of an inorganic or organic highly absorbent (e.g., superabsorbent) material to improve the absorbency of the absorbent body. The absorbent body 40 may, for example, contain 5-95% by weight of the highly absorbent material, and preferably includes about 10-30% by weight of the highly absorbent material to improve effectiveness. Suitable inorganic highly absorbent materials include, for example, absorbent clays and silica gels. Organic highly absorbent materials may include natural materials such as agar-agar, pectin, guar gum, and peat moss, as well as synthetic materials such as synthetic hydrogel polymers. Such hydrogel polymers include, for example, carboxymethylcellulose, alkali metal salts of polyacrylic acids, polyacrylamides, polyvinyl ethers, hydroxypropylcellulose, polyvinylmorpholinone, polymers and copolymers of vinylsulfonic acid, polyacrylates, polyacrylamides, polyvinylpyridine, and the like. Other suitable polymers include hydrolyzed acrylonitrile-grafted starch, acrylic acid-grafted starch, and isobutylene-maleic anhydride copolymers, and mixtures thereof. The hydrogel polymers are preferably slightly cross-linked to impart the desired degree of water insolubility to the material. Cross-linking may be accomplished, for example, by irradiation or by covalent, ionic, van der Waals, or hydrogen bonding. Suitable materials are available from various suppliers, such as Dow Chemical Company, Hoechst Celanese Corporation, Allied-Colloid, and Stockhausen. The superabsorbent material typically can absorb at least about fifteen times its weight in water. and can preferably absorb at least about 25-50 times its weight in water.

The highly absorbent material may be distributed or otherwise incorporated into the absorbent body 40 using various techniques. For example, the highly absorbent material may be incorporated into a separate carrier layer layered with a body of air-laid cellulose fibers. Alternatively, the highly absorbent material may be distributed substantially evenly throughout the fibrous mass comprising the absorbent body. The material may also be distributed unevenly among the fibers, thus forming, for example, a generally continuous gradient with either an increasing or decreasing concentration of the highly absorbent material as determined by considering the concentration from the body side of the absorbent body 40 toward the outside of the absorbent body. The highly absorbent material may also comprise one or more separate layers or strips which are optionally isolated from the fibrous material of the absorbent body 40.

The highly absorbent material itself can be present in various particle shapes. Particles of highly absorbent material can, for example, have the shape of grains, flakes, fibers or the like.

Optionally, a substantially hydrophilic tissue wrap 42 may be used to help maintain the integrity of the air-laid fibrous structure of the absorbent body 40. The tissue wrap layer is typically placed around the absorbent body over at least the two major opposing surfaces of the absorbent body and is made of an absorbent cellulosic material such as creped batting or high wet strength tissue. According to one aspect of the invention, the Tissue wrap may be designed to provide a wicking material layer which assists in the rapid distribution of liquid throughout the mass of absorbent fibers comprising the absorbent body. According to a further aspect of the invention, the wrap layer material on one side of the absorbent fiber mass may be bonded to the wrap layer on the opposite side of the fiber mass. The bonding points are located at individual, separate areas and extend through the thickness of the fiber mass. In such a configuration, the wrap is effectively shaped to form a plurality of individual "funnels" or "stitches" which may assist in directing liquids into the interior of the fiber mass and ensure faster absorption of the liquid. An effective embodiment may further comprise a plurality of holes or openings formed at least partially through the thickness of the fiber mass. The embodiment is designed such that the bonding of the oppositely positioned layers of wrap material occurs through these openings or holes. The openings limit the amount of intervening fiber material and allow for a more direct bond between the wrap layers. The bonding may include adhesive bonds, sonic bonds, thermal bonds, or the like.

In particular embodiments of the invention, spacing means, such as at least one liquid-permeable separating layer 50, may be disposed oppositely adjacent between the upper layer 30 and the absorbent body 40. An effective spacing means is designed to be liquid-permeable while retaining and absorbing as little liquid as possible. For this reason, the spacing means may provide a relatively dry region between the wetted absorbent body and the upper layer 30. maintained. Likewise, the spacing means may advantageously be designed in such a way as to provide a regular or irregular network of voids or channels to facilitate the movement of air within the diaper. In the embodiment shown, the separation layer 50 is made from a nonwoven web of natural fibers and/or synthetic polymer fibers. Suitable fibers include, for example, acrylic fibers, nylon fibers, and blends thereof. Other suitable polymer fibers may, for example, be made from a polyolefin such as polyethylene, polypropylene, polyester, or blends thereof. For example, the web may be a composite of polypropylene fibers and polyethylene fibers. The polymer fibers are typically hydrophobic, but may be treated with a selected amount of surfactant to regulate the wettability thereof. However, when treated with surfactant, the separation layer should be even more hydrophilic than the material comprising the absorbent body 40. The presence of an effective amount of the surfactant can advantageously improve the rate of movement of liquid into the absorbent body 40 during initial releases of liquid into the absorbent article.

Thickness is an important parameter for the release layer 50 and can be measured under both low contractile pressure (0.207 kPa) and high contractile pressure (50.37 kPa). A suitable apparatus for carrying out the thickness measurement under high pressure (50.37 kPa) is a "Testing Machine, Inc., Model 49-70 Bulk Testing Apparatus" with a 1.59 cm diameter plate. The thickness measurement under low pressure (0.207 kPa (0.03 psi)) can be carried out with a thickness measuring apparatus with a round plate with a diameter of 7.62 cm (3 inches) to apply a pressure of 0.207 kPa (0.03 psi) to a sample positioned on a non-elastic rigid surface. For example, a suitable device for measuring bulk density under low pressure included a Starrett® type granite surface plate available from the LF Starrett Company of Aphol, Massachusetts. The device further included a 7.62 cm diameter movable platen driven by a Clipper air valve foot pedal assembly, catalog #3C30A2-S, available from the Linemaster Switch Corporation of Woodstock, Connecticut. The thickness indication was provided by a Digimatic Indicator manufactured by the Mitutoyo Manufacturing Company Limited of Japan and distributed by the MTI Corporation of Paramus, New Jersey. The range of the indicator is 0.0025-5.08 cm (0.001-2.0 inches).

To provide a desired level of effectiveness, the release layer 50 has a dry bulk density (at 0.207 kPa) of at least about 0.04 cm, and preferably has a dry bulk density in the range of about 0.07-0.51 cm. When measured at 50.37 kPa, the dry bulk density of the release layer 50 is at least about 0.025 cm, and preferably in the range of about 0.025-0.1 cm. If the release layer 50 is too thin, it may not provide adequate separation and spacing between the top layer 30 and the absorbent body 40. Similarly, a composite bulk density of the top layer 30 and release layer 50 that is too thin may result in insufficient separation and spacing between the absorbent body 40 and the wearer's skin. Therefore, the composite bulk density (at 0.207 kPa) of the separating layer 50 and the upper layer 30 is at least about 0.078 cm, and preferably their composite bulk density is in the range of about 0.1-0.6 cm. When measured at 50.37 kPa, the composite bulk density of the top layer 30 and the separating layer 50 is at least about 0.039 cm, and preferably is in the range of about 0.039-0.12 cm.

The separation layer may have a basis weight of at least about 25 g/m². According to particular aspects of the invention, the basis weight is at least about 34 g/m² and is preferably at least about 55 g/m² to ensure improved effectiveness. According to further aspects of the invention, the basis weight is no more than about 170 g/m² and is preferably in the range of about 55-170 g/m². To maintain a desired effectiveness of the separation layer 50, the separation layer should be able to maintain its spacing function even after it has been wetted by urine or other aqueous liquids discharged by the wearer and even after it has been subjected to the characteristic pressures exerted by the wearer during use.

According to a particular aspect of the invention, the separating layer is designed to maintain a desired degree of dryness. In particular, the material of the separating layer can be designed to advantageously have a desorption ratio of at least about 100. The desorption ratio can be determined as follows:

A 5.08 x 5.08 cm (2 in. x 2 in.) sample of a separating layer is weighed and then immersed in a 0.9% saline solution for one minute. The saline solution is adjusted with Tween® 20 to ensure a surface tension of approximately 0.00055 N/cm (55 dynes/cm). Tween 20, also referred to as polyoxyethylene sorbitan ester 20, is a surfactant manufactured by ICI Americas, Inc. of Wilmington, Delaware and is made from a mixture of laurate esters of sorbitol and sorbitol anhydride.

The sample is removed from the saline solution, placed in a clamp to hang in a vertical position from a ring stand, and allowed to drain for 1 minute. After this 1 minute draining period, the sample and any retained liquid are weighed. The sample is then placed on a desorption pad for one hour under a pressure of 3.45 kPa applied over substantially the entire surface of the sample. The sample and any liquid remaining therein are weighed after the 1 hour desorption period. The desorption pad is 5.08 cm x 5.08 cm (2 inches x 2 inches) in size and comprises a pulp fluff web having a basis weight of about 800 g/m² with about 15% by weight of a superabsorbent polyacrylate hydrogel material.

The desorption ratio is determined as follows:

Desorption ratio = A/B

where:

A = Weight increase of the sample after the soaking/draining process.

B = Weight increase of the sample after the desorption process of 1 hour.

The fibers comprising the release layer 50 are formed to have a denier in the range of about 0.167-1.67 tex (about 1.5-15 d), and preferably have a denier in the range of about 0.167-0.67 tex (about 1.5-6 d). Furthermore, the release layer 50 is formed to have a basis weight of at least about 34 grams per square meter (gsm), and preferably has a basis weight in the range of about 55-170 gsm. The release layer may also have a bulk density (at 0.207 kPa) which is in the range of about 0.03-0.5 g/cm³ and preferably in the range of about 0.07-0.5 g/cm³ to provide further advantages.

To maintain the desired effectiveness of the separating layer 50, the separating layer should be able to maintain its spacing function as described above even when wetted by urine or other aqueous fluids discharged from the wearer. Thus, the wet compression recovery value of the separating layer 50 is at least about 65%. Preferably, the wet compression recovery value is at least about 80%, more preferably at least about 85% to provide improved performance.

The compression recovery value is a measure of the "springiness" or elasticity of the material and can be determined by the following procedure. The original thickness (t0) of the release liner material is first measured under a restraint pressure of 0.689 kPa (0.1 psi). After this measurement, the pressure on the release liner material is gradually increased to 20.7 kPa (3 psi). The compression pressure is then gradually decreased until the restraint pressure again reaches 0.689 kPa (0.1 psi). At this point, the bulk density is again measured at the restraint pressure of 0.689 kPa (0.1 psi) to obtain a recovery thickness value (tR). The compression recovery value is then determined according to the following formula:

Compression recovery value (CRV) = (tR/t�0)·100%

A suitable device for determining the compression recovery value is a "Standard Model Compressometer" sold by Frazier Precision Instrument Co. of Gaithersburg, Maryland. For the purpose of For compression recovery tests, the device design features a base with a diameter of 2.54 cm (1 inch).

When the determination described above is made using a dry release liner, a dry compression recovery value is obtained. When the determination described above is made using a release liner substantially saturated with distilled water, a wet compression recovery value is obtained. According to a particular aspect of the invention, the release liner has a dry CRV of at least about 65% and a wet CRV of at least about 65%. In a preferred embodiment of the invention, both the dry CRV and the wet CRV are at least about 80% to improve efficiency.

According to another aspect of the invention, the absorbent garment comprises a plurality of two or more separating layers disposed adjacently opposite one another and located between the top layer 30 and the absorbent body 40. In particular, there may be individual separating layers between the top layer and the absorbent body 2-5. For example, Fig. 2 representatively shows an embodiment having three separating layers 50, 52, 54. It has been found that a plurality of separating layers can advantageously provide improved effectiveness in reducing the amount of moisture on the wearer's skin. It appears that the interspaced spaces between the individual separating layers can contribute to separating the wearer's skin from the wet absorbent and to improved movement of water vapor away from the moistened skin, but no commitment to any particular theory is intended. In a particular embodiment of the invention, the separating layers can be used to Promote the circulation of drier ambient air into the diaper through the breathable panel 70.

The individual release layers are distinct and separate from one another, but may be bonded together at selected, localized locations to maintain the integrity of the assembly. For example, the individual release layers 50, 52, 54 may be point bonded together at localized, separate locations 46. The multiple release layers have a total composite bulk density (measured dry at 0.207 kPa) of at least about 0.04 centimeters, and preferably have a total composite bulk density in the range of about 0.07-0.51 cm. Measured at 50.37 kPa, the composite release layers have a total dry bulk density of at least about 0.025 cm, and preferably have a total dry bulk density in the range of about 0.025-0.1 cm. Additionally, the total bulk density (at 0.207 kPa) of the topsheet 30 in combination with the multiple release layers is at least about 0.078 cm 3 , and preferably the total composite bulk density is in the range of about 0.1-0.6 cm 3 . Measured at 50.37 kPa, the composite bulk density of the topsheet 30 and the multiple release layers is at least about 0.039 cm 3 , and preferably the composite bulk density is in the range of about 0.039-0.12 cm 3 . The multiple release layers in combination should have a composite desorption ratio of at least about 100 when tested by the desorption method described above. The multiple release layers can have an effective composite basis weight of at least about 25 g/m 2 . In particular aspects of the invention, the effective composite basis weight is at least about 34 g/m 2 and is preferably at least about 55 g/m 2 . According to further aspects of the invention, the effective composite basis weight is not more than about 170 g/m² and is preferably in the range of about 55-170 g/m². The multiple release layers may further have an effective bulk density (measured at 0.207 kPa) in the range of about 0.03-0.5 g/cm³ and preferably in the range of about 0.07-0.5 g/cm³.

The separation layers may extend entirely or partially over the adjacent surface area of the absorbent body 40. Preferably, the separation layers are located over the intermediate portion 16 of the disposable diaper 10 and are aligned substantially centrally side to side with respect to the longitudinal centerline 18 of the disposable diaper. The separation layers extend over about 35-100% of the total longitudinal length of the diaper 10 and over about 50-100% of the width of the diaper as measured at the narrowest area of the intermediate portion 16. In the embodiment of the invention shown, the separation layers extend transversely over a width of about 12.7 cm and extend longitudinally over a length of about 38.1 cm.

According to a particular embodiment of the invention, the separation layer or layers may be limited to a front portion of two thirds of the diaper. In yet another embodiment of the invention, the separation layers may be limited to a central region of 35-60% of the longitudinal length of the diaper 10 and may be longitudinally offset toward the front waistband portion of the diaper.

In the embodiment of the invention using multiple release layers, the individual release layers can extend over the same or over different areas. For example, release layer 50 can cover a larger surface area than release layer 52, and release layer 52 can cover a larger surface area than the separating layer 54. Likewise, the individual separating layers may be made from different materials. For example, all of the separating layers could be made from a different polymer fiber, or could be made from the same polymer fiber but have different basis weights.

The multiple release liners have a composite dry compression recovery value of at least about 65%, and preferably have a composite dry CRV of at least about 80%. In addition, the multiple release liners have a composite wet CRV of at least about 65%, and preferably have a composite wet CRV of at least about 80% to improve effectiveness.

It is believed that the presence of the separating layer(s) can advantageously provide more effective spacing of the wearer's skin from the wet absorbent pad as well as improved circulation of moist air and water vapor away from the area immediately adjacent to the wearer's skin, although no particular theory is intended. In conventional designs, having the wet absorbent body closer to the skin can provide an occlusive effect which helps to trap and hold the moist air against the skin. However, the inclusion of an effective separating layer can help to provide more open spaces and irregular channels which allow moist air to more readily escape the wetted area of the absorbent body and which allow drier air; for example, from the waistband portions of the article; to circulate into the wetted area. The drier air can then help reduce any excess hydration of the skin.

A breathable panel 70 that is substantially liquid impermeable but vapor permeable may be located in at least one waistband portion of the diaper 10 to provide various advantages and improvements. Particular embodiments of the invention may optionally include the breathable panel in combination with the separating layer(s) as described above. In the embodiment shown, the breathable panel is configured to extend from the backsheet 20 at the front waistband portion 12 of the diaper. Alternatively, a breathable panel may be located at the rear waistband portion 14 of the diaper, or a breathable panel 70 may be located at both the front and rear waistband portions of the diaper 10. The breathable web 70 is substantially liquid impermeable, but significantly more vapor permeable than the backsheet 20. In particular, the breathable web may comprise a material having a moisture vapor transmission rate (WVTR) of at least about 2000 g/m²/24 hrs. Preferably, the breathable web has a WVTR of at least about 4000 g/m²/24 hrs., and more preferably has a WVTR of at least about 5000 g/m²/24 hrs. to improve performance. Additionally, the breathable web 70 has an effective breathable area of at least about 22 cm². In particular aspects of the invention, the effective breathable area is at least about 45 cm², and preferably the effective breathable area is in the range of about 45-400 cm² to provide additional benefits.

The effectiveness of the breathable web can be advantageously improved by at least a portion of the breathable web with respect to a selected waistband region of the absorbent body 40. It has been found that such coverage in overlying relationship can more effectively reduce skin hydration and better cooperate with each separating layer(s) to assist in removing moisture from the area adjacent to the wearer's skin and circulating drier air to the area of skin covered by the wet absorbent body. The configuration of the present invention typically provides a substantially fluid impermeable backing in the central, crotch region of the diaper and confines the breathable panel portions to the waistband portions of the diaper which are relatively far from the target areas of the absorbent body which typically experience direct wetting by the wearer. Therefore, smaller amounts of the relatively expensive breathable panel material are required. It should be noted that prior art diaper designs have utilized outer shells made entirely of a breathable but fluid impermeable material such as microporous polymer film. Such designs were configured to allow water from a wetted absorbent pad to evaporate through the breathable outer cover, drying the pad and restoring its absorbency. However, the diaper designs were expensive to manufacture and can cause a cold and clammy feel to the diapers due to moisture evaporating from the surface of the outer cover.

In contrast to conventional designs, it was found that the aim of reducing hydration of the skin by limiting the breathable area of the outer shell so that it is at the far waistband sections of the diaper over the absorbent body. It has been found that controlling the movement of air through the dry portions of the absorbent can be more effective in reducing hydration of the skin. With the article of the invention, moisture from the wearer's skin can still move easily out of the diaper and dry replacement air can flow more effectively into the diaper to the area adjacent to the skin. The replacement air can be substantially prevented from moving into the diaper along a path through the wetted absorbent. Consequently, the replacement air is less likely to become excessively moist before reaching the wearer's skin.

It has been found that additional advantages can be achieved by an arrangement combining the breathable web 70 with one or more separating layers. One of the advantages, for example, is that with such an arrangement, the breathable web can be effective even if its vapor permeable area is reduced to an area of only about 5 cm² (about 0.785 in²). The vapor permeable area of the web 70 can therefore be in the range of about 5-400 cm². Consequently, the cost of an operative absorbent article can be further reduced by using an even smaller amount of the liquid impermeable but vapor permeable material.

If the breathable panel 70 is partially covered or occluded by another substantially vapor impermeable component of the diaper 10, the area of the breathable panel 70 should be increased appropriately to compensate for the concealment of the breathable area by the occluding component. For example, if adhesive tapes are used as a fastening means for the diaper, a tape attachment region 37 made from a plastic film may be attached to the outer surface of the breathable panel 70 to provide a resealable adhesive tape system. While the plastic film may be vapor permeable or vapor impermeable, placement of the tape attachment region 37 over the breathable panel may over-occlude a portion of the breathable panel and may require increasing the breathable surface area at other locations on the panel 70. Similarly, if the diaper 10 includes a hook and loop fastener system, such as a Velcro fastener, the absorbent material may be disposed over an outwardly facing surface of the breathable panel 70. While the absorbent material itself may be vapor permeable, the adhesive or other bonding system used to attach the absorbent material over the breathable panel 70 may be substantially vapor impermeable. To reduce occlusion of the web 70, an irregular, open pattern of the adhesive or other bonding mechanism may be used to attach the receiving material to the breathable web. For example, when using an adhesive, an open pattern of sprayed droplets or sprayed filaments may be used to attach the component to the breathable web.

The breathable web 70 may be made from a microporous polymer film, such as a "Grade PMP-1" film manufactured by Mitsui Toatsu Chemical, Inc., Tokyo, Japan. Alternatively, the breathable web 70 may be made from a nonwoven material, such as a spunbond or meltblown web of synthetic polymer fibers.

According to a particular aspect of the invention, the breathable web 70 is made from a calendered fiber composite web having a barrier layer of fine fibers and a reinforcing layer of coarse fibers. The barrier layer and the reinforcing layer are firmly bonded together by melting or bonding the reinforcing fibers into the barrier fibers, and the reinforcing layer is formed to form the outward-facing surface of the composite web.

The reinforcement layer of the composite can be a web of hydrophobic fibrous material arranged to provide a basis weight of the web in the range of about 10-35 g/m². The reinforcement layer has a grab tensile strength in the range of about 1500-10,000 g/2.54 cm (g/in) and is bonded with a point bond pattern that covers between about 3-20% of the surface area of the reinforcement layer. The barrier layer of the composite is a web of hydrophobic fibrous material arranged to provide a basis weight in the range of about 10-50 g/m². The barrier layer is made from a plurality of randomly deposited, substantially continuous, hydrophobic thermoplastic fibers that are partially bonded together. Such a web can be made by melt blowing a web of thermoplastic polymer microfibers having an average cross-sectional diameter of about 3.0 micrometers or less.

The barrier layer and the reinforcement layer are firmly bonded together with an irregular bonding pattern of thermal bonds, sonic bonds, heat or pressure activated adhesive resin or similar. This interlayer bonding pattern covers an area in the range of approximately 3-20% of the surface area of the composite sheet. A suitable composite membrane shall have a porosity value in the range of approximately 3-15.25 m³/minute/m² and shall be able to withstand a body of water of at least 70 cm of water for a period of 5 seconds with a visible seepage of not more than one drop (0.05 cm³) of water.

As representatively shown in Figure 2, the breathable panel 70 may optionally be a separate component that adjoins and extends laterally and longitudinally across the front waistband portion 12 of the diaper 10. The breathable panel 70 may extend across the entire cross-sectional width of the diaper 10, as shown in the embodiment shown. Alternatively, the breathable panel 70 may extend partially across the cross-sectional width of the diaper. For example, the breathable panel may comprise a sheet component that extends across a notch or depression or a "window"-like opening formed in the layer of backsheet material. To provide the desired amount of breathable surface area, the panel 70 may have a longitudinal dimension in the range of about 2-18 centimeters. In accordance with a particular aspect of the invention, the breathable panel 70 extends at least about 10%, and preferably at least about 15%, of the longitudinal length of the absorbent body to improve performance. According to another aspect of the invention, the breathable panel may be configured to extend no more than about 40%, and preferably no more than about 30%, of the length of the absorbent body to provide additional benefits. The illustrated embodiment of the panel 70 extends about 20% of the longitudinal length of the absorbent body 40 from the end edge at the front waistband of the absorbent body. While the illustrated embodiment shows a breathable panel extending all the way to the end edge at the waistband of the diaper article, it should of course be noted that that the extent of the panel 70 along the longitudinal direction of the diaper may optionally terminate just before the end edge at the waistband portion.

Referring to Figure 3, the effectiveness of the present invention can be enhanced by designing the absorbent body 40 to include a moisture transfer region 44 which is disposed in operative, adjacent registration with the breathable web 70. The moisture transfer region has a relatively low moisture retention capacity compared to the other portions of the absorbent body where liquid is normally held and stored. The moisture transfer region can, for example, comprise a substantially hydrophobic, non-wettable fibrous material, such as a layer or other suitable mass of polyester fibers.

According to a particular aspect of the invention, the moisture transfer region has a moisture retention index of no more than about 40 g. Preferably, the moisture transfer region has a moisture retention index of no more than about 30 g, and more preferably a moisture retention index of no more than about 20 g. The low moisture retention index of the moisture transfer region can advantageously help to limit the occlusive effect caused by the presence of retained liquids. Therefore, water vapor can more easily escape from the spaces adjacent to the wearer's skin.

The moisture transfer region can also advantageously be designed to have a wicking index of not more than about 0.2 g. Preferably, the Moisture transfer region preferably has a wicking index of no more than about 0.1 g, and more preferably a wicking index of no more than about 0.05 g to improve effectiveness. The relatively low wicking index of the moisture transfer region helps limit the presence of liquid that could impede the movement of water vapor away from the wearer's skin.

According to another aspect of the invention, the moisture transfer region may have a composite structure. For example, the moisture transfer region may comprise a multilayer composite of one or more cellulosic tissue layers, nonwoven polymer web layers, woven fabric layers, or combinations thereof. Each of the layers may be wettable or nonwettable, as desired.

In one embodiment of the invention, the density of the moisture transfer zone is no more than about 0.1 g/cm³, and according to another embodiment of the invention, the density of the moisture transfer zone is no less than about 0.001 g/cm³. Preferably, the moisture transfer zone has a density in the range of about 0.001-0.05 g/cm³ to improve efficiency. According to another aspect of the invention, the moisture transfer zone can have an average basis weight of no more than about 550 g/m², and preferably has an average basis weight in the range of about 5-300 g/m² to improve efficiency. To further contribute to its efficiency, the moisture transfer zone can be formed with a bulk density which, when measured dry at 1.38 kPa (0.2 psi), is no less than about 0.051 cm (about 0.02 in). Preferably, the Moisture transfer region has a bulk density of not less than about 0.203 cm (about 0.08 in), and more preferably has a bulk density of not less than about 0.254 cm (about 0.10 in) to better assist in reducing hydration of the skin. A particular aspect of the invention features a configuration wherein the moisture transfer region has a Frazier air permeability value of at least about 15.25 m³/min/m², and another aspect of the invention features an arrangement wherein the moisture transfer region has a Frazier air permeability value in the range of about 15.25-30 m³/min/m².

The moisture transfer region 44 is located at a waistband portion of the absorbent body 40 and can be arranged in a variety of suitable shapes. For example, the moisture transfer region can be formed to extend from a longitudinal end of the absorbent body and across the entire cross-sectional width of the absorbent (Figs. 3 and 7). Alternatively, the moisture transfer region can extend only partially across the width of the absorbent body, as shown in Figs. 8 and 10. In the embodiment of Fig. 10, the moisture transfer region occupies a generally rectangular, notch-shaped area formed in the absorbent body 40, but the occupied area can optionally be formed by any other suitable regular or irregular shape, such as the circle shown in Fig. 8.

In an optional configuration of the invention, the absorbent body 40 may have a single opening or a plurality of openings 43 through the thickness of the absorbent body, with at least a portion of the openings disposed in operative registration with the breathable web 70 (Fig. 3). The For example, apertures may be circular and have diameters in the range of about 0.5 - 2.0 cm. Apertures of other different shapes may also be used to provide an effective moisture transfer area to assist in the function of the breathable sheet 70.

Other components of the diaper 10, such as the topsheet 30, release layers (50, 52, 54) and other liquid-conducting layers, may, but need not, extend beyond the area occupied by the moisture transfer region 44. In the illustrated embodiment, these liquid-conducting layers are formed to extend generally adjacent to and opposite the moisture transfer region.

The article of the invention may advantageously be designed to reduce excessive hydration of the wearer's skin and the relative humidity in the environment adjacent to the wearer's skin. According to a particular aspect of the invention, the breathable web is formed from a material which provides a test relative humidity (TRH) value of not more than about 80%. Preferably, the breathable web is designed to provide a TRH value of not more than about 75% to improve performance. The reduced relative humidity values may help to dehydrate the skin and return to its normal environmental hydration level.

According to a further aspect of the invention, the diaper 10 can advantageously be designed to provide an average net skin hydration value (average net SHV) of not more than about 0.8 g/m² in 2 minutes. Preferably, the diaper is designed to designed to provide an average clean SHV of no more than about 0.5 g/m² in 2 minutes for improved effectiveness. Such average clean SHVs indicate lower skin wetness levels compared to the excessive skin wetness levels that can occur in conventional diapers after they are wetted. The lower skin wetness levels can help make the skin less susceptible to abrasion and to chemical or biological irritants.

A suitable method for determining the WVTR (water vapor transmission rate) value of a material is ASTM E96-80. For the purposes of the present invention, 7.62 cm (3") diameter circular samples are cut from the test material and a control material, Celguard® 2500 (Hoechst Celanese). Five samples are provided for each material. The test pan is a No. 60-1 Vapometer crucible, available from Thwing-Albert Instrument Company, Philadelphia, Pennsylvania. One hundred milliliters of water is poured into each Vapometer crucible, and each of the test material and control material samples is positioned over the open top of an individual crucible. Screw-on flanges are tightened to form a seal around the edges of the crucible, exposing the associated test material or control material to the ambient atmosphere over a circular area (an open, exposed area of approximately 33.17 cm2) 6.5 cm in diameter. The crucibles are placed in a forced air oven set at 37.78ºC (100ºF) for 1 hour to equilibrate. The oven is a constant temperature oven through which outside air is passed to prevent water vapor buildup inside. An example of a suitable forced air oven is one available from Blue M Electric Co., Blue Island, Illinois. "Blue M Power-O-Matic 60" furnace. After equilibration is complete, the crucibles are removed from the furnace, weighed and immediately returned to the furnace. After six hours, the crucibles are removed from the furnace and weighed. The preliminary WVTR test value is calculated as follows:

WVTR test value = (grams weight loss over 6 hours) (g/m²/24 hrs) · 1263

The relative humidity in the oven is not specifically controlled.

Under predetermined, fixed conditions of 37.78ºC (100ºF) and ambient relative humidity, the WVTR for Celguard 2500 was determined to be 5000 g/m²/24 hrs.

Consequently, Celguard 2500 serves as a control sample in each test and the previous test values are corrected to the specified conditions using the following equation:

WVTR value = (WVTR test value/WVTR control value) · 5000 g/m²/24 hrs.

Celguard 2500 is a 0.0025 cm thick film made of a microporous polypropylene.

The Frazier air permeability values referred to in this specification can be determined using a "Frazier Air Permeability Tester" (Frazier Precision Instrument Co., Gaiterhersburg, Maryland) and "Method 5460, Federal Test Methods Standard No. 191A". For the purposes of the present invention, the test is conducted on a 20.32 cm x 20.32 cm (8'' x 8'') sample.

The test relative humidity (TRH) value of a structure can be determined by the following TRH test device and procedure:

As shown schematically in Figure 4, the TRH test apparatus includes a temperature controlled chamber 80 and a relative humidity (RH) container 82. The temperature controlled chamber 80 measures 45.72 cm x 68.58 cm x 91.44 cm (18" x 27" x 36") to enclose a volume of about 0.283 m³ (10 ft³) and is maintained at a temperature of 32.22ºC (90ºF). The relative humidity in the chamber depends on ambient conditions.

The RH container is open topped and constructed of 1/4" thick plexiglass with external dimensions of 4.5" x 4.5" x 5.5" and a volume of about 80 in3 (1310.96 cm3) when a sample is in position. To reduce the volume of air in the RH container, the container may be partially filled with plastic balls (0.75" diameter). The container has a circular opening 84 on one side through which an RH probe 86 is pushed and has a narrow rib 88 about 1/4" from the top. The test sample 92 is held on the rib. The RH and temperature probes used to measure and record relative humidity and temperature are manufactured by Solomat Corporation, Stamford, Connecticut. Specifically, the instruments that can be used are the "MPM2000 Modular System" with the "M2013 Modumeter", the "MPM Data Logger", the "155RH Fast Response Probe" for measuring relative humidity and the "PP206 SF Flexible Patch Thermo-couple Probe" for measuring the temperature.

A sufficient number of 10.16 x 10.16 cm (4'' x 4'') absorbent squares 90 are provided, each absorbent square being made of about 800 g/m² basis weight of wood pulp fibers and about 15% by weight of superabsorbent particles, such as particles of a polyacrylate superabsorbent. A tissue wrapper of absorbent cellulosic material is positioned on either side of each absorbent square.

Samples of Test Materials 92 are cut into 12.7 cm x 12.7 cm (5'' x 5'') squares. An additional test sample of Celguard 2500 (Hoechst Celanese) with a WVTR of 5000 g/m²/24 hrs is provided and serves as a control.

The relative humidity container, the Solomat relative humidity and temperature sensors, the absorbent squares, the samples of the test materials and a quantity of isotonic saline solution (0.9 wt.% sodium chloride) are allowed to equilibrate in the temperature control chamber.

A selected absorbent square is removed from the temperature control chamber, weighed and then returned to the chamber. The temperature and relative humidity in the RH container are recorded and the Solomat Data Logger is turned on to begin recording relative humidity at one minute intervals. After two relative humidity readings have been taken, the absorbent square and saline solution are removed from the chamber. A saline solution is poured over the top of the absorbent square in an amount approximately six times the weight of the absorbent square. square. The absorbent is then placed in the RH container and a sample of test material is placed over the top of the container. A plexiglass holder 96 is used to hold the sample on the container. The data logger reports relative humidity measurements at one minute intervals for sixty minutes and the temperature in the RH container is recorded. After the sixty minute test time, the sample of test material is removed and the relative humidity and temperature within the RH container are allowed to re-equilibrate with chamber conditions prior to testing another sample. After all samples have been tested, the data can be transferred from the data logger to a personal computer, printed and recorded. The test relative humidity value (TRH) for a particular sample corresponds to the relative humidity value measured at the sixty minute point.

A suitable procedure for determining the Moisture Retention Index of a section of Absorbent Body Material is as follows:

Referring to Fig. 5, a suitable test device for determining the moisture retention index comprises an electronic balance 102 accurate to 0.01 g and having a capacity of at least 1000 g. The balance also includes a digital signal output for use with a digital-to-analog converter 104 and a recorder 106. A second electronic balance is used to weigh the test samples. A suitable electronic balance is, for example, a "Mettler PC2200" manufactured by Mettler Instrument Company, a company with offices in Hightstown, New Jersey. The digital-to-analog converter should be compatible with the electronic balance 102 and the recorder 106. In the embodiment shown, the digital-to-analog converter is, for example, a "Mettler GC47 D/A Converter". A suitable recording device is, for example, a "Fisher Recordall Series 5000", which is available from Houston Instrument, a company with offices in Austin, Texas.

The device also includes a 500 milliliter suction bottle 108 for holding an appropriate reservoir supply of artificial urine 110. The suction bottle is provided with a #4 rubber stopper 112 and a 17.78 cm (7") long glass trachea 114 having an inner diameter of 5.58 mm (0.22 inches). The trachea 114 passes through a bore formed through the center of the stopper 112 and is inserted until approximately 12.7 cm (5") of the trachea protrudes from the inner surface of the stopper.

5A and 5B representatively show an enlarged side view and top view, respectively, of an absorbency testing chamber 116. The test chamber is made of a suitable material, such as lucite, and has a generally square base area measuring 10.16 cm x 10.16 cm (4" x 4"). The chamber includes a base member 138 measuring 10.16 cm x 10.16 cm (4" x 4") and a 1.59 cm (5/8") wall member 140 along each of the four sides of the base member. A cover 124 having a weight of 125 grams is configured for placement over the sample contained in the chamber 116. The cover extends over a generally square area and is configured to be slightly smaller than the top opening into the chamber 116. Therefore, the cover can adequately prevent evaporation of moisture and can easily slide along the walls of the chamber to apply a selected pressure to the upper portion of a sample therein. A stepped circular depression 142 is formed in the top of the base 138 and the channel 144 extends through the base to an outlet tube 136 having an inner diameter of 0.635 cm (0.25"). The channel 144 directs liquid into the bottom of the well 142 where it is then directed through a multi-channel transfer disk to a test sample 126. Within the test chamber, a 3.175 cm (1.25") diameter multi-channel plate 122 made of lucite sits in the well 142 on the step therein. The multi-channel plate includes seven channels, each 3 mm in diameter, with one channel located in the center of the plate 122 and the remaining six channels arranged radially from the center channel and equally spaced peripherally along a 3.016 cm (about 1 3/16") diameter circle around the center channel. The seven channels are positioned 0.95 cm (3/8") apart from center and the plate 122 is centrally located within the chamber 116. A 0.635 cm (0.25 inch) inside diameter plastic tubing, such as R3603 Tygon tubing, connects the outlet tube 130 of the reservoir bottle 108 to the tube 136 entering the base 138. The total length of the plastic tubing 128 is approximately 2.25 m (7.5'); however, the exact lengths are not critical. The tubing lengths should allow for easy use of the device, but should not be excessive. A control valve, such as a polypropylene two-way stopcock 132, regulates the flow of fluid through the plastic tubing 128. The stopcock 132 has a 4 millimeter bore so as not to overly restrict fluid flow. Laboratory jacks are used to regulate the vertical positioning of the test device components. In particular, the laboratory lift 118 supports the electronic balance 102 and the reservoir bottle 108, while the laboratory lift 120 supports the test chamber 116 and the components contained therein. Laboratory gantry jacks 148 and 149 may be used for any major, coarse adjustments to the vertical position of the test apparatus components.

The test device should be clean and free of bacterial contaminants and salts that may have been excreted from the artificial urine. No handling of the test equipment should occur during the test procedure. In the event of removal or handling of the tubing, an equilibration period of approximately 1 hour should allow for the tubing to be relieved of any stress experienced by the tubing. This equilibration period should also be allowed for when filling the reservoir bottle 108. The tubing should not be touched during the test procedure. The absorbent material being tested should be pre-treated at "standard" conditions of 50±2% RH and 23±1ºC. The appropriate body side of the absorbent material should be placed opposite the multi-channel plate 122. All cleaning agents used to clean any component of the test device should be completely removed so as not to affect the surface tension of the artificial urine used to perform the test.

Prior to the testing procedure, the reservoir bottle 108 is filled with artificial urine and a portion of the liquid is drained through the tubing to remove any air bubbles from the tubing and from the fluid passages in the test device. The drained artificial urine is drained and the tap is closed to stop the flow of liquid. The reservoir bottle is then refilled. The plastic tubing 128 should not have any sharp bends or kinks that could impede the flow of liquid and alter the test results.

Before the test procedure, the device is also adjusted to establish a zero point. First, the chamber 116 is leveled by placing a spirit level of suitable size in the Center of the chamber and aligned by gently pushing on the appropriate side of the laboratory lift 120. The front and back of the chamber 116 should also be aligned. At this point, the test chamber 116 can be mounted on the laboratory lift 120. The tap 132 is then opened to allow fluid to flow and a slightly concave meniscus is formed in each of the seven 3 mm channels in the plate 122 by adjusting the height of the laboratory lift 120. A zero point is obtained when each of these channels contains artificial urine with a slightly concave meniscus and an air bubble is maintained at the bottom of the glass tube 114 within the reservoir bottle 108. The tap 132 is then closed to stop the flow of fluid and the chamber 116 is checked to ensure that it is still aligned. The device is then allowed to equilibrate for 3-6 hours. This equilibration time is not necessary if the test device is in continuous use and no liquid change or addition has occurred. The recorder 106 is turned on and set to record at zero when the electronic balance 102 is zeroed.

The balance setting of the test device is controlled by positioning the cover 124 on the chamber 116 and closing the tap 132. The electronic balance 102 is then zeroed and the recorder is turned on. The test device is balanced when the reading of the weight of the absorbed fluid is stable at zero. Preferably, the reading of the weight of the absorbed fluid should not vary by more than plus or minus 0.03 g in 15 minutes.

Test specimen 126 is in the form of a disk with a 7.62 cm (3") diameter. The specimen is weighed to the nearest 0.01 gram and the weight is recorded. The thickness of the specimen is measured using a 7.62 cm (3") diameter plate under a restraining pressure of 1.38 kPa (0.2 psi).

A piece of filter paper, such as Whatman No. 4 filter paper, with a diameter of 7.62 cm (3 inches) is placed centrally over the multi-channel plate 122 within the chamber 116. The stopcock 132 is then opened to pre-wet the filter paper and remove any air bubbles. It should be noted that a new piece of filter paper is used for each test sample. The stopcock is then closed to stop the flow of liquid and excess liquid is blotted from the edges of the filter paper. The center of the filter paper, however, is not blotted to avoid the formation of any air bubbles. The areas around the filter paper 134 and the cover 124 should each be dry. The stopcock 132 is opened and the electronic balance 102 is zeroed following stabilization.

The test is initiated by simultaneously placing and centering the absorbent sample 126 over the filter paper 134 with the cover 124 resting on the sample and turning on the recorder 106. The test sample 126 is then allowed to absorb fluid for a test period of 30 minutes. At the end of this period, the stopcock 132 is closed and the recorder 106 is turned off. The final reading of the electronic balance is recorded on the recorder paper to serve as a control of the recorder data. The moisture retention index represents the value in grams of the artificial urine collected from Test Sample 126 during the 30-minute test period.

A suitable procedure for determining the wicking index of a single, generally homogeneous material or a composite material is as follows:

Referring to the apparatus representatively shown in Figure 6, the apparatus for conducting the wicking test includes a chamber 150 having a base measuring 10.16 cm x 10.16 cm (4" x 4"). A test sample 152 having a 7.62 cm (3") diameter is weighed using an electronic balance, such as a Mettler PC2200 balance accurate to 0.01 gram. A 10.16 cm (4") x 10.16 cm (4") piece of 0.0254 mm (1.0 mil) thick polyethylene film is placed on the bottom of the chamber 150, and a 7.62 cm (3") diameter piece of retentive material 154 is placed on top of the polymer film. The retention material is made of 3 layers of composite fibrous web material and superabsorbent particles. Each layer of composite material is made of wood pulp fluff and 2% by weight of meltblown polypropylene fibers. About 1.69 g (range of 1.64-1.73 g) of the superabsorbent material is contained in the composite material. The resulting retention material 154 has a total thickness of 1.9 cm (0.75") and a total basis weight of 900 g/m². The total dry weight of the retention material is about 4.84 g (range of 4.70-4.95 g), of which 35% by weight is superabsorbent material. The particles of the superabsorbent material are composed of polyacrylate hydrogel polymer, for example SANWET IM-5000 manufactured by Hoechst Celanese.

After loading the retention material with 24.2 g (mL) of artificial urine (5 grams/gram liquid load), a 10.16 cm x 10.16 cm (4'' x 4'') piece of screening material 156 is positioned on the retention material 154. The screen material is a fiberglass mesh screen with the screen strands generally arranged in a pattern which is generally a square grid pattern with 18 openings per linear 2.54 cm (inch) (324 openings per 6.45 cm² (in²)) and a screen thickness of about 0.028 cm.

The test sample 152 is then positioned on the screen 156 and a cover 158 having a weight of 125 grams is positioned over the entire test sample 152 to impart a pressure of 0.268 kPa (0.039 psi). The cover extends over a generally square area and is designed to be slightly smaller than the top opening into the chamber 150. Therefore, the cover can adequately prevent evaporation of moisture and can easily slide between the walls of the chamber to impart the selected pressure to the top of a sample therein. Thirty minutes after applying the weight 158 to the test sample 152, the test sample is removed from the chamber 150 and weighed to the nearest 0.01 gram. The difference between the dry sample weight and the "wet" sample weight after the 30 minute test period is the amount of fluid wicked from the loaded retaining material 154 into the test sample 152. The amount of fluid wicked (in grams) is referred to as the wicking index.

Skin hydration levels are determined by measuring total transepidermal water loss (TEWL) and can be determined by the following test procedure:

The test is performed on partially toilet trained children who have no lotions or ointments on their skin and who have not been bathed in the last 2 hours before the test. Half of the selected group of children are to wear the test diaper first and the control diaper second. The other half of the group of children are to wear the control diaper first and the test diaper second.

Each test diaper is weighed before and after use to check the volume of fluid released into the diaper. A felt pen is used to mark an "X" at the target area in the diaper, with the "X" located 7.62 cm (3'') below the top front end of the absorbent pad and centered side to side. TEWL measurements are taken using an evaporimeter, such as an Evaporimeter EP1 device distributed by Servomed AB, Stockholm, Sweden. Each test measurement is taken over a two-minute period, with TEWL values taken once per second (120 TEWL values total). The digital output of the Evaporimeter EP1 device indicates the amount of transepidermal water loss (TEWL) in g/m2/hr. Skin hydration values (SHV) are in units of the total amount of water lost per unit area measured during the two-minute sample period and are calculated as follows:

A preliminary measurement of the skin hydration value is taken on the lower abdomen of the child in a section of the diaper corresponding to the target area using the evaporimeter to obtain the initial skin hydration value of the child's skin at the target area of the Diaper is then placed on the child. Before the diaper is placed on the child, a tube is positioned to direct a flow of fluid to hit the previously marked target area. After the diaper is placed, 120 milliliters of adjusted saline solution (surface tension adjusted to 0.00055 N/cm (55 dynes/cm) using Tween 20) is added in two additions of 60 milliliters each at a rate of 15 milliliters/second. The time between additions is 30 seconds.

The child wears the diaper for 30 minutes, after which two skin hydration measurements are taken. A baseline measurement is taken on the thigh in an area of skin not covered by the diaper. This baseline SHV is compared to the previous SHV measurement to demonstrate that the child is not perspiring. Perspiration may cause the SHV measurement to be falsely high. A test skin hydration measurement is also taken on the lower abdomen area according to the target area marking on the diaper. The used diaper is then weighed and the child is allowed to play in his/her cloth underwear for 25-30 minutes. The testing procedure is then repeated for each child using the diaper type (test or control diaper) that the child has not yet worn.

The control diaper provided a standard baseline for comparing the performance of the diaper form tested and evaluated. In the tests conducted for the purposes of the present invention, the control diaper comprised an outer cover backing of 0.0254 mm (1 mil) thick polypropylene and a topsheet of a spunbonded polypropylene nonwoven web having a basis weight of 27 g/m². The topsheet had 0.206 cm (0.081 in) diameter apertures extending across a central region of the topsheet. formed therethrough with approximately 76 openings per 6.45 cm² (in²). The central region extended 8.89-12.7 cm (3.5-5") wide and along the entire length of the diaper. An absorbent pad of wood pulp fluff having a basis weight of about 800 gsm containing about 15% by weight of superabsorbent polyacrylate polymer particles was located between the backsheet and the topsheet. The pad also included a tissue cover having an absorbent layer of a creped cellulose wadding material. A fluid transport layer of a spunbonded fibrous web of polypropylene fibers having a basis weight of about 42 gsm was located between the topsheet and the absorbent pad. The control diaper was applied to the child using adhesive tape fasteners and had elastic pleats at the leg and waist areas of the diaper.

Data for all children who increased saline loading are discarded. The value reported for the average clean SHV (grams/m2 in two minutes) is calculated as the average for all children of the post-wear skin hydration value taken on the lower abdomen (target area marker) minus the skin hydration value taken on the thigh.

The clear skin hydration value is determined as follows:

Pure SHVi = Y-Z

where: Y = skin hydration value measured at the target area marker of an individual child

Z = baseline skin hydration value measured on the leg, thigh of an individual child

SHVi = Skin hydration value for individual child

Then:

Average net SHV =

where: N = number of children in the test

The percentage reduction in skin hydration is determined as follows:

% Reduction =

where: C = Pure SHVi for control diaper

D = Pure SHVi for test diaper

N = number of children in the test

The following examples are intended to provide a more detailed understanding of the invention. The specific materials and parameters are examples and are not intended to specifically limit the scope of the invention.

example 1

A disposable diaper was prepared having a backsheet with a liquid and vapor impermeable base portion and an attached liquid impermeable but vapor permeable web portion. An absorbent body was housed between a liquid permeable topsheet and the backsheet, and separating layers were located between the absorbent body and the topsheet. The diaper also had a hook closure system.

The base portion of the backsheet comprised a conventional 0.0254 mm (1 mil) thick polyethylene film which was liquid and vapor impermeable. The breathable panel was attached extending from the end of the base portion and formed the front waistband portion of the backsheet. The material used for the breathable panel was a laminate of 34 gsm calendered fine fiber polypropylene meltblown fabric and 24 gsm polypropylene spunbond fabric which was heat bonded to a bond area of approximately 12%. The meltblown side of the fabric was positioned adjacent to the absorbent body and the spunbond side was positioned on the outside of the diaper. The WVTR value of this fabric material was approximately 5000 g/m²/24 hrs. The breathable panel spanned the entire width of the diaper and extended longitudinally approximately 13 cm from the front edge of the diaper.

The absorbent body was made from a mixture of cellulose fluff and superabsorbent polyacrylate particles. The basis weight of the fluff was about 800 g/m² and the mixture contained about 15% by weight of superabsorbent particles. The absorbent body also contained a tissue cover made of highly wet-strength tissue.

The top layer was designed to be positioned on the wearer's body. Therefore, the 27 g/m² The material of the upper layer, made of spunbond polypropylene nonwoven fabric, was soft and protected against sores.

In the hook and loop fastener system, the receiving material was applied to the breathable sheet 70 by applying adhesive only around the edges of the material to prevent occlusion of the breathable sheet.

The separating layers were three layers of 42 g/m² spunbonded polypropylene (126 g/m² total) that had a composite bulk density of 0.11 cm³ (measured at a pressure of 0.207 kPa) and a bulk density of 0.11 g/cm³. The separating layers were 12.7 cm wide and 16.5 cm long, with the leading edge of the layers located 5 cm from the leading edge of the absorbent. The layers were ultrasonically point bonded to each other and to the top layer at intervals of approximately 5 cm around the edges of the layers.

The diaper had an average clean Swr of approximately 0.3 g/m2 in two minutes. Compared to the conventional control diaper described above, this represented a 69% reduction in skin hydration.

Example 2

A disposable diaper was prepared having a backsheet with a liquid and vapor impermeable base portion and an attached liquid impermeable but vapor permeable web portion. An absorbent body was housed between the backsheet and a liquid permeable topsheet, and separating layers were located between the absorbent body and the topsheet.

The base portion of the backsheet comprised a conventional 0.0254 mm (1 mil) thick polyethylene film which was liquid and vapor impermeable. The breathable panel was attached to the end of the base portion and extended from it to form the front waistband portion of the backsheet. The material used for the breathable panel was a 34 gsm calendered fine fiber polypropylene meltblown nonwoven fabric. The WVTR of this fabric was approximately 5000 gsm/24 hrs. The breathable panel extended across the entire width of the diaper and extended longitudinally approximately 13 cm from the front edge of the diaper.

The separators comprised three layers of 42 g/m² polypropylene spunbond (126 g/m² total) having a composite bulk density of 0.11 cm (measured at a pressure of 0.207 kPa) and a bulk density of 0.11 g/cm³. The separators were 12.7 cm wide and 16.5 cm long, with the leading edge of the separators located 5 cm from the leading edge of the absorbent body. The separators were ultrasonically point bonded to each other and to the top layer at approximately 5 cm intervals around the edges of the layers.

The diaper had an average clean SHV of approximately 0.2 g/m2 in two minutes. Compared to the conventional control diaper, this represented a 70% reduction in skin hydration.

Example 3

This article was the same as Example 2, except that the length of the separating layers was 24 cm, with the leading edge of the layers being located at the leading edge of the absorbent body.

The diaper had an average clean SHV of approximately 0.45 g/m2 in two minutes. Compared to the control diaper, this represented a 56% reduction in skin hydration.

Example 4

This article was the same as Example 3, except that the release liners were a bonded carded polyester web obtained from H.D.K., a company in Rogersville, Tennessee. The web was made of fibers having a denier of about 0.61 tex (about 5.5) bonded together with about 16.6% powdered adhesive. The composite basis weight of the three layers was about 108 g/m², the composite bulk density was 0.40 cm², and the composite bulk density was 0.03 g/cm³.

The diaper had an average clean SHV of approximately 0.6 g/m2 in two minutes. Compared to the control diaper, this represented a 52% reduction in average clean SHV.

Example 5

A diaper was made having a backsheet with a liquid and vapor impermeable base portion and an attached liquid impermeable but vapor permeable web portion. An absorbent body was housed between the backsheet and a liquid permeable topsheet.

The base portion of the pad comprised a conventional 0.0254 mm (1 mil) thick polyethylene film which was impermeable to liquids and vapors. A breathable sheet was attached to the end of the base portion and extended from it to form the front Waistband portion of the backing. The breathable panel was made of 34 g/m² calendered fine fiber polypropylene meltblown nonwoven fabric. The WVTR of this fabric was approximately 5000 g/m²/24 hrs. The breathable panel extended across the entire width of the diaper and extended longitudinally approximately 13 cm from the front edge of the diaper.

The diaper had an average clean SHV of about 0.5 g/m2 in two minutes. Compared to the control diaper, this represented a 40% reduction in skin hydration.

Example 6

This article is the same as Example 1, with the exception that the separating layers extend from the front waist edge of the absorbent body to the rear waist edge of the absorbent.

Example 7

This article is the same as that of Example 6, except that the release layers are composed of a bonded carded polyester web manufactured by H. D. K. The web is made of fibers having a tex (denier) value of about 0.61 (about 5.5) bonded together with about 16.6% adhesive powder. The composite basis weight of the three release layers is about 103 g/m², the composite bulk density is about 0.09 cm³, and the composite bulk density is about 0.12 g/cm³.

Example 8

A diaper with a liquid and vapour impermeable backing layer; a liquid-permeable upper layer; an absorbent body accommodated between the upper layer and the backing layer and separating layers arranged between the absorbent body and the upper layer.

The separating layers are three layers of 42 g/m² polypropylene spunbond (per layer; total 126 g/m²) that have a composite bulk density of 0.11 cm and a bulk density of 0.11 g/cm3. The separating layers are 12.7 cm wide and extend the entire length of the absorbent body.

Example 9

This article is the same as Example 8, except that the separating layers are made of a woven cotton material having a bulk density of 0.076 cm, a bulk weight of 186 g/m², and a bulk density of 0.245 g/cm³. Since this cotton material has approximately the same hydrophilicity as the material comprising the absorbent body, the separating layers can hold fluid close to the skin and result in skin hydration values that are higher than those measured when no separating layers are present.

Example 10

This article is the same as Example 6, except that the breathable sheet is made of a microporous polyethylene film such as PMP-1 from Mitsui Toatsu. This film material has a WVTR of about 4000 g/m²/24 hrs.

Example 11

This article is the same as Example 6 except that a breathable panel is located at both the front waistband portion and the back waistband portion of the diaper.

Example 12

This article is the same as Example 6, except that the entire backing is made of a vapor permeable material such as Mitsui Toatsu's PMP-1 with a WVTR of about 4000 g/m²/24 hrs. As moisture evaporates through the backing 20, the diaper may feel cold and clammy.

Example 13

This article is the same as Example 6, except that it has a moisture transfer region. This is achieved by either making the region of the absorbent body behind the breathable web less dense than the rest of the absorbent body or by providing openings through the thickness of the absorbent.

Example 14

A diaper garment 200 representatively shown in Fig. 7 comprises a backsheet 20, a topsheet 30 and an absorbent body 40 disposed between the backsheet and the topsheet. The backsheet 20 comprises a breathable web 70 joined to form an extension of the backsheet. The absorbent body 40 has a moisture transfer region 44 joined to extend from a longitudinal end of the absorbent body. Optionally, between the absorbent body 40 and the upper layer 30, one or more separating layers 50 are arranged.

In the embodiment shown, the absorbent body 40 is an absorbent composite having a shock control layer 202, a tissue layer 204, and a retention region 206. The shock layer 202 is a fibrous material that rapidly absorbs and temporarily holds rapid discharges of liquid and transports the liquid from the initial entry point to other parts of the absorbent body. The representative embodiment of the shock layer 202 shown is made of a Hydrofil material having a basis weight of 200 g/m² and a bulk density of 0.218 cm (0.086") (at 1.38 kPa (0.2 psi)). The Hydrofil material is a meltblown macrofiber nonwoven web available from Allied-Signal, a company having offices in New York, New York. Alternatively, the impact layer 202 may comprise a nonwoven web of polyethylene fibers having a web basis weight of 200 gsm and a bulk density of 1.82 cm (0.72") (at 1.38 kPa (at 0.2 psi)).

The illustrated embodiment of the containment region 206 comprises 3 layers of a composite nonwoven web and superabsorbent material particles. The superabsorbent material is made from a polyacrylate hydrogel polymer and comprises 35% by weight of the containment region. The composite layers have a total basis weight of 900 gsm and a total bulk density of 0.75" (at 0.2 psi). The composite material is made from 50-63% by weight wood pulp fluff and 2-15% by weight meltblown Hydrofil fibers or meltblown polypropylene fibers. The high wet strength tissue 204 has a basis weight of 21 gsm and a bulk density of 0.009" (0.022 cm).

The front waistband of the diaper's absorbent body has a moisture transfer area 44 comprising a substantially hydrophobic, non-wettable polyester fiberfill material, a material that is typically used for padding. The fiberfill material has a basis weight of about 180 g/m² and a density of about 0.0417 g/cm³ (at 1.38 kPa (at 0.2 psi)). The moisture transfer area measures 2.54 cm (1") along the diaper's length and 11.25 cm (4.5") along the diaper's cross-dimension, thus covering an area of 28.57 cm² (4.5 in²).

A vapor permeable web 70 disposed over the moisture transfer area is a composite of an inner layer of calendered meltblown fibers and an outer layer of a Guilford knit fabric. In the embodiment shown, the Guilford fabric is a "Guilford part 19903 loop material" which is a polyester warp knit fabric of two-needle bar construction. The fabric is made of 40/13 polyester yarn (front bar) and 2.22 tex (20 denier) per filament monofilament (back bar) sprayed with Rohm & Haas AC-73 binder. The knit fabric has a basis weight of 108.5 g/m² (3.2 ounces/in²) and is available from Guilford Mills, a company with offices in Greensboro, North Carolina. The binding material is available from the Rohm & Haas Company, a company with offices in Philadelphia, Pennsylvania.

Example 15

A diaper garment was formed having the structure described in Example 14. However, the diaper of this example comprised a top layer of a Guilford 19903 active ingredient layer and had a release layer from a further layer of an active ingredient Guilford 19903 located next to the upper layer.

Compared to a standard control diaper, the diaper designed according to this example exhibited a 43% reduction in the skin hydration value.

Example 16

A diaper garment was formed having the structure described in Example 15. However, the diaper was modified to have a moisture transfer region in the form of a 5.08 cm (2") diameter opening formed in the SAM/fluff (liquid retention material) of the absorbent body, as representatively shown in Figure 8. The opening was positioned so that the edge of the opening was about 2.54 cm (1") from the adjacent waistband edge of the absorbent body, and the removed liquid retention material was replaced with a polyester fiberfill material having a basis weight of about 180 g/m2 and a bulk density of about 0.43 cm (about 0.17") measured at 1.38 kPa (0.2 psi). Compared to a standard control diaper, the diaper designed according to this example showed a 27% reduction in the skin hydration value.

Example 17

A diaper garment was formed having the structure described in Example 15. However, the diaper of this example was modified to have a moisture transfer region comprising a multilayer composite of a 200 gsm layer of 0.218 cm (0.086") thick Hydrofil bumper material and 2 layers of 21 gsm tissue material as representative shown in Fig. 9. Compared to a standard control diaper, the diaper constructed according to this example had a 41% reduction in skin hydration value.

Example 18

A diaper garment was formed having the structure described in Example 15. However, the diaper of this example was modified to have a moisture transfer region in the form of a generally rectangular notch formed in the absorbent body 40. At the location of this notch, the moisture transfer region was made from a 200 gsm web of meltblown polyethylene fibers having a thickness of 0.18 cm (0.072") and 2 layers of 21 gsm tissue material, as representatively shown in Figure 10. The moisture transfer region had an area of 16.13 cm (2.5 in). Compared to a standard control diaper, the diaper formed according to this example had a 29% reduction in skin hydration value.

Example 19

An absorbent composite was formed with 2 layers of Guilford 19903 loop material. Each layer had a basis weight of 108 g/m² and a bulk density of 0.06 cm (0.026'') (at 1.38 kPa (0.2 psi)). The Guilford loop material formed the top layer component of the absorbent composite. Overlying the layers of Guilford loop material were 2 layers of Hydrofil bumper material. Each of these layers of bumper material had a basis weight of 200 g/m² and a bulk density of 0.218 cm (0.086'') (at 1.38 kPa (0.2 psi)). Overlying the bumper material layers was a 21 g/m² tissue material layer. A The containment material layer region was located above the tissue material and formed the outermost region of the absorbent composite. The containment material was made of 3 layers of composite material containing 35% superabsorbent particles by weight. The composite material had a total basis weight of 900 g/m² and a total bulk density of 1.9 cm (0.75") (at 1.38 kPa (0.2 psi)).

WVTR testing of samples of the absorbent composite material loaded with different amounts of artificial urine yielded the following data:

Loading (g/g) WVTR (g/m² per 24 hours)

0 3113

2 2792

3 2335

5 2274

6 1865

7 2037

8 1851

9 1737

The graph of Fig. 11 shows representatively the above measurement points correlated with a quadratic equation. From these data it can be concluded that even a loading of 3 g fluid/g absorbent can reduce the WVTR of the absorbent composite to a level which may not be sufficient to ensure a desired level of skin dryness. Preferably the WVTR is at least about 3500 g/m² per 24 hours.

For the purposes of this example, the WVTR test procedure is slightly modified to account for the liquid introduced into the absorbent composite: After filling the WVTR vessel with 100 mL of distilled water and equilibrating in the oven for 1 hour, the WVTR vessel is weighed (without the top section/screws). The sieve and test sample are then placed on the vessel and the top section is screwed into place. After the sample is loaded with artificial urine and equilibrated for 3 minutes at room temperature, the vessel is placed in the oven according to the conventional procedure. After removal from the oven, the top section, sieve and sample are removed from the vessel. The vessel with the remaining water is then weighed and the WVTR value is determined.

Example 20

Three samples of retention material were made of composite fiber material and superabsorbent particles. The retention material had a basis weight of about 900 g/m², a thickness of about 1.9 cm (0.75") (at 1.38 kPa (0.2 psi)), and contained about 35% superabsorbent by weight. The samples had the following properties:

Sample No. Moisture Retention Index

1 92,95

2 92.06

3 89.53

Example 21

Four samples were prepared, each sample containing the retention material of Example 20, a Tissue layer on the retention material, a layer of Hydrofil bumper material on the tissue, and a layer of Guilford loop material (19903) on the bumper material. The tissue had a basis weight of about 21 g/m² and a thickness of about 0.022 cm (about 0.009"). The bumper material had a basis weight of about 200 g/m² and a thickness of about 0.218 cm (about 0.086") and the Guilford loop material had a basis weight of about 108 g/m² and a thickness of about 0.066 (about 0.026"). The samples of this example had the following properties: Sample No. Moisture Retention Index Wicking Index

Example 22

Four samples were prepared, each sample comprising a tissue layer, a layer of Hydrofil bumper material on the tissue, and a layer of Guilford loop material (19903) on the bumper material. The tissue had a basis weight of about 21 g/m² and a thickness of about 0.022 cm (about 0.009"). The bumper material had a basis weight of about 200 g/m² and a thickness of about 0.218 cm (about 0.086") and the Guilford loop material had a basis weight of about 108 g/m² and a thickness of about 0.066 (about 0.026"). The samples of this example had the following properties: Sample No. Moisture Retention Index Wicking Index [* Display 27 minutes]

Example 23

Four samples were prepared, each sample comprising a layer of tissue, a layer of polyester fiberfill on the tissue, and a layer of Guilford loop material (19903) on the butt material. The tissue had a basis weight of about 21 g/m² and a thickness of about 0.022 cm (about 0.009"). The fiberfill had a basis weight of about 180 g/m² and a thickness of about 0.43 cm (about 0.17"), and the Guilford loop material had a basis weight of about 108 g/m² and a thickness of about 0.066 cm (about 0.026"). The samples of this example had the following properties: Sample No. Moisture Retention Index Wicking Index

Claims (56)

1. An absorbent article (10) generally defined by a front waistband portion (12), a rear waistband portion (14) and an intermediate portion (16) connecting the front waistband portion to the rear waistband portion, the article comprising: a substantially vapour impermeable backing layer (20); a liquid-permeable upper layer (30) which is arranged opposite to the back layer (20); an absorbent body (40) for storing absorbed Liquid, wherein the absorbent body is located between the back layer (20) and the upper layer (30) and has an absorbent material which ensures a degree of moisture retention therein for storing absorbed liquid, wherein the absorbent body (40) characterized by the fact that it has a moisture transfer zone region (44), wherein the moisture transfer zone region (44) has a relatively lower degree of moisture retention capacity compared to other regions of the absorbent body (40) where the liquid is normally stored; and wherein the absorbent article is further characterized by a vapor permeable web (70) which is substantially liquid impermeable and is joined to the backsheet (20) in at least one waistband portion of the article, the vapor permeable web (70) being disposed overlying in register with at least a portion of the moisture transfer zone (44). 2. The absorbent article of claim 1, wherein the moisture transfer zone (44) has a moisture retention index of no more than 40 g. 3. The absorbent article of claim 1, wherein the vapor permeable web is sufficiently liquid impermeable to withstand a body of water of 70 cm for 5 seconds with a visible leakage of not more than 0.05 ml of water. 4. Absorbent article according to one of the preceding claims, wherein the vapor permeable web (70) comprises a material having a moisture vapor transmission rate (WVTR) value of at least 2000 g/m²/24 hrs, preferably at least 4000 g/m²/24 hrs, and most preferably at least 5000 g/m²/24 hrs. 5. Absorbent article according to one of the preceding claims, further comprising one or more separation layers (50, 52, 54) located between the top layer (30) and the absorbent body (40). 6. Absorbent article according to claim 5, wherein the separating layers (50, 52, 54) and the top layer (30) have a total composite bulk density (at 0.207 kPa) which is at least 0.078 cm and preferably in the range of 0.1-0.6 cm. 7. Absorbent article (10) according to claim 1, comprising: one or more separating layers (50, 52, 54) which are located between the upper layer (30) and the absorbent body (40), the separating layers (50, 52, 54) ensuring an effective liquid transfer between the upper layer (30) and the absorbent body (40) and forming spacers which comprise a substantially hydrophobic material and have a total bulk density in a range of 0.07-0.51 cm (at 0.207 kPa); and wherein the vapor-permeable web (70) extends over an area in the range of 5-400 cm². 8. Absorbent article according to one of the preceding claims, wherein the vapor permeable panel (70) is formed in a front waistband portion and/or a rear waistband portion of the backsheet (20). 9. An absorbent article according to any preceding claim, wherein the vapor permeable web (70) comprises a calendered, meltblown nonwoven web. 10. Absorbent article according to one of the preceding claims, wherein the moisture transfer region (44) comprises a mass of hydrophobic fibers, preferably a mass of polyester fibers. 11. Absorbent article according to one of the preceding claims, wherein the moisture transfer region (44) has a moisture retention index of not more than 30 g and preferably not more than 20 g. 12. An absorbent article according to any preceding claim, wherein the moisture transfer region (44) has a wicking index of no more than 0.2 g, preferably no more than 0.1 g, and most preferably no more than 0.05 g. 13. Absorbent article according to one of the preceding claims, wherein the moisture transfer region (44) comprises a composite material, preferably a multi-layer composite material. 14. Absorbent article according to one of the preceding claims, wherein the moisture transfer region (44) comprises a fibrous web having a density in the range of 0.001-0.05 kg/cm³ and a basis weight in the range of 5-300 g/m². 15. Absorbent article according to one of the preceding claims, wherein the vapor permeable web (70) is made of a material which ensures a test value of relative humidity (TRH) of not more than 80%, preferably not more than 75%. 16. Absorbent article according to one of the preceding claims, further comprising spacer means (50, 52, 54) located between the upper layer (30) and the absorbent body (40), the spacer means ensuring effective liquid transfer between the upper layer and the absorbent body, the spacer means comprising a substantially hydrophobic material, wherein the spacing means and the upper layer together have a bulk density of at least 0.078 cm. 17. An absorbent article according to claim 16, wherein the spacing means comprises one or more separating layers (50, 52, 54) of fibrous material having a composite bulk density of at least 0.04 cm. 18. Absorbent article according to one of claims 5 to 17, in which one or more of the separating layers (50, 52, 54) comprise an active agent. 19. Absorbent article according to one of the preceding claims, wherein the vapor permeable web (70) extends over a vapor permeable area of at least 5 cm² in total. 20. Absorbent article according to one of the preceding claims, wherein the material of the vapor permeable web (70) extends along 10-40% of the length of the absorbent body. 21. Absorbent article according to one of the preceding claims, wherein the absorbent body (40) comprises a moisture transfer region (44) having a composite basis weight of not more than 550 g/m², which lies adjacent to the vapor permeable web (70). 22. Absorbent article according to one of the preceding claims, wherein the moisture transfer region (44) of the absorbent body (40) has a density of not more than 0.1 g/cm³. 23. An absorbent article according to any preceding claim, wherein the moisture transfer region (44) is disposed in operably register with the vapor permeable web (70) and has an average basis weight in the range of 5-300 g/m² and/or an average density in the range of 0.001-0.05 g/cm³ and/or a bulk density of at least 0.51 cm (about 0.02 inches). 24. Absorbent article (10) according to claim 1 comprising: one or more liquid-permeable separating layers (50, 52, 54) located between the upper layer (30) and the absorbent body (40), the separating layers (50, 52, 54) enabling fluid transfer between the upper layer (30) and the absorbent body (40), the separating layers (50, 52, 54) comprising a substantially hydrophobic material and the separating layers and the upper layer having a total bulk density of at least 0.078 cm (at 0.207 kPa). 25. The absorbent article of claim 24, wherein the vapor permeable web (70) comprises a material having a water vapor transmission rate (WVTR) value of at least 2000 g/m²/24 hrs, more preferably at least 4000 g/m²/24 hrs, and most preferably at least 5000 g/m²/24 hrs. 26. Absorbent article according to one of claims 24 or 25, in which the separating layers (50, 52, 54) have a total composite bulk density of at least 0.04 cm (at 0.207 kPa). 27. Absorbent article according to one of claims 24 to 26, wherein the separating layers (50, 52, 54) and the upper Layer have a total composite bulk density which is at least 0.078 cm (at 0.207 kPa) or preferably in the range of 0.1-0.6 cm. 28. Absorbent article according to one of claims 24 to 27, in which the vapor permeable web (70) extends over a vapor permeable area of at least 5 cm² in total. 29. Absorbent article according to one of claims 24 to 28, wherein the vapor permeable panel (70) is formed in a front waistband portion (12) and/or a rear waistband portion (14) of the backsheet. 30. The absorbent article of any of claims 24 to 29, wherein the vapor permeable web (70) comprises a calendered, meltblown nonwoven web. 31. Absorbent article according to one of claims 24 to 30, wherein the separating layers (50, 52, 54) comprise 1-5 layers of nonwoven web material. 32. The absorbent article of claim 31, wherein the separating layers (50, 52, 54) are layers of spunbond fibrous web material comprising polyolefin fibers. 33. The absorbent article of claim 32, wherein each of the spunbonded fiber webs has a total basis weight of at least 34 g/m². 34. An absorbent article according to claim 32, wherein one or more of the spunbond fiber web layers comprises polypropylene fibers and has a basis weight in Range of 55-170 g/m² and a bulk density of 0.03 -0.5 g/cm³ (at 0.207 kPa). 35. The absorbent article of claim 34, wherein the polypropylene fibers have a denier in the range of 1.5-6d. 36. Absorbent article according to one of claims 24 to 35, in which the absorbent body (40) has a plurality of openings (43) through its thickness, and in which at least a portion of the openings are in operative registration with the permeable web (70). 37. Absorbent article according to one of claims 24 to 36, wherein the absorbent body (40) has a moisture transfer region (44) which is in operative registration with the vapor permeable web (70), the moisture transfer region (44) having a density in the range of 0.001 - 0.05 g/cm3 and a basis weight in the range of 5-300 g/m2. 38. Absorbent article according to one of claims 24 to 37, wherein the vapor permeable web (70) is made of a material which ensures a test value of relative humidity (TRH) of not more than 80%, preferably not more than 75%. 39. Absorbent article according to one of claims 24 to 38, wherein the separation layers (50, 52, 54) are limited to a front portion of two thirds of the absorbent article (10). 40. An absorbent article according to any one of claims 24 to 38, wherein the separation layers (50, 52, 54) are limited to a central portion of 35-60% of the absorbent article. 41. An absorbent article according to any one of claims 24 to 40, wherein the article comprises a plurality of individual separation layers (50, 52, 54), two or more of which are joined together at selected spaced locations (46). 42. An absorbent article according to claim 41, wherein the separation layers (50, 52, 54) are joined together at individual locations arranged in a selected pattern. 43. Absorbent article (10) according to claim 1 comprising: Spacing means (50, 52, 54) located between the upper layer and the absorbent body (40), the spacing means ensuring effective fluid transfer between the upper layer and the absorbent body, and the spacing means comprising a substantially hydrophobic material and having a total bulk density of at least 0.04 cm. 44. Absorbent article according to claim 43, wherein the vapor permeable web (70) comprises a material having a water vapor transmission rate (WVTR) of at least 2000 g/m²/24 hrs, and/or extends over an area in the range of 5-400 cm². 45. An absorbent article according to any one of claims 43 or 44, wherein the material of the vapor permeable web (70) extends along 10-40% of the length of the absorbent body starting from an end edge at the front waistband of the absorbent body (40). 46. Absorbent article according to one of claims 43 to 45, wherein the absorbent body (40) has a Moisture transfer region (44) which is adjacent to the vapor permeable web (70) and has a basis weight of not more than 550 g/m² and/or a density of not more than 0.1 g/cm³. 47. Absorbent article (10) according to claim 1 comprising: a vapor permeable web (70) joined to the backsheet (20) in at least one waistband portion (12, 14) of the article, the vapor permeable web (70) comprising a material that is substantially liquid impermeable and has a water vapor transmission rate (WVTR) of at least 2000 g/m²/24 hrs and extends over a web area of at least 22 cm², and an absorbent body (40) which is located between the back layer (20) and the upper layer (30) and with a region of the absorbent body (40) underneath arranged in cover with the vapor-permeable web (70). 48. The absorbent article of claim 47, wherein the vapor permeable web extends over an area of at least 45 cm2. 49. An absorbent article according to claim 47 or 48, wherein the absorbent body (40) has a moisture transfer region (44), the region being in operative registration with the vapor permeable web (70) and having an average basis weight in the range of 5-300 g/m². 50. Absorbent article according to one of claims 47 to 49, wherein the moisture transfer region (44) has an average density in the range of 0.001-0.05 g/cm3. 51. Absorbent article (10) according to claim 1, comprising: a vapor permeable web (70) which is substantially liquid impermeable and is joined to the backsheet (20) in at least one waistband portion (12, 14) of the article, the vapor permeable web (70) comprising a material having a moisture vapor transmission rate (WVTR) of at least 2000 g/m²/24 hrs and extending over an area of at least about 22 cm²; and an absorbent body (40) located between the backing layer (20) and the top layer (30) and having a moisture transfer region (44) located in operably opposed registration with the vapor permeable web, the moisture transfer region having one or more openings (43) therethrough to ensure a Frazier air permeability value of at least 15.25 m³/min./m². 52. An absorbent article according to claim 51, wherein the apertured moisture transfer region (44) provides a Frazier air permeability value in the range of 15.25-30 m³/min/m². 53. Absorbent article according to claim 51 or 52, wherein the openings (43) are substantially round and have an average diameter in the range of 0.5-2.0 cm. 54. An absorbent article according to any preceding claim, wherein the moisture transfer zone region (44) comprises a substantially hydrophobic, non-wettable fibrous material having a basis weight in the range of about 5-300 g/m² and a density of no more than 0.1 g/cm³, the non-wettable fibrous material being configured to limit the presence and wicking of liquid therein and to limit occlusion of the non-wettable fibrous material by liquid. 55. Absorbent article according to one of the preceding claims, wherein the moisture transfer region (44) comprises a substantially hydrophobic, non-wettable fibrous material having a basis weight in the range of 5-300 g/m² located in one or more openings spaced entirely from longitudinally opposite waistband edges of the absorbent body (40) and formed by the dimension of the thickness of the absorbent body (40), the non-wettable fibrous material being designed to limit the presence and wicking of liquid therein and to limit occlusion of the non-wettable fibrous material by liquid. 56. An absorbent article according to any preceding claim, wherein the moisture transfer zone region (44) comprises a substantially hydrophobic, non-wettable fibrous material having a basis weight in the range of 5-300 g/m², which is designed to extend over an entire waistband edge of the absorbent body (40), the non-wettable fibrous material being designed to limit the presence and wicking of liquid therein and to occlude the non-wettable fiber material by liquid.